I mean proof is in the stats, as far as how the development community has taken to vB5.
vB4 was released as Gold in December of 2009. In December of 2011, two years after it's release, these were the stats. (source,
https://web.archive.org/web/20111226...play.php?f=198 and
https://web.archive.org/web/20111225...play.php?f=212)
vBulletin 4.x Add-ons: 1359
vBulletin 4.x Template Modifications: 473
vBulletin 4.x Styles: 313
Now lets look at vB5, two years after it's release.
vBulletin 5.x Products & Extensions: 53
vBulletin 5.x Template Modifications: 21
vBulletin 5.x Styles: 21
Also two years after vB5 is released, the market share of vB5 installs is only at 1.4% of all vBulletin instillation's, which shows, even the member base using vBulletin don't like the direction it went in. (source,
https://tools.digitalpoint.com/cookie-search)
Not to mention that many users/coders have moved away from vBulletin to other platforms.